Analysis of Heterosis of Winter Brassica rapa in Gansu Province,Northern China

Twelve hybrids produced by 9 parents were used to analyze heterosis of winter rapeseed.The results showed that cold tolerance,agronomic traits and yield potentiality had higher heterosis,but there were significant differences among different combinations.Compared with the parents,hybrids had better cold tolerance represented by winter survival rates;plant height and number of branches had significant heterosis and the average of over-high parent heterosis rate was 3.72%(0.34%-14.29%) for plant height and 8.56%(0.00%-18.75%) for number of branches.For the yield components,8 crosses gave 12.79% of over-high parent heterosis for siliques per plant.Four crosses showed over-high parent heterosis on seeds per silique,but only 3 crosses showed over-high parent heterosis on 1 000-seed mass(0.00%-1.68%).Eleven' crosses gave 22.34% of over-high parent heterosis for seed yield on average.The results showed that winter survival rates,plant height and numbers of branches had significant heterosis,The heterosis of siliques number per plant made the biggest contribution to heterosis of seed yield,while 1 000-seed mass and seeds per silique made little to seed yield.